1. Field of the Invention
The present invention relates to an ink exchange apparatus for use in a flexographic printer etc. in which an ink exchange at the time of a color change accompanying with an order change is automatically made.
2. Description of the Prior Art
An ink exchange apparatus used in a flexographic printer in the prior art is described with reference to FIGS. 4(a), (b) and 5. A usual ink exchange apparatus used in a flexographic printer, as shown in FIG. 4(a), comprises an ink circulation and supply mechanism for circulating ink between one of ink tanks and a printing unit and supplying the ink to the printing unit; an ink tank exchange mechanism for connecting a joint portion to the ink tank of said ink circulation and supply mechanism selectively to one of the ink tanks; and a wash liquid supply mechanism for supplying a wash liquid to said ink circulation and supply mechanism at the time of washing of said ink circulation and supply mechanism.
FIG. 4(a) is a perspective view of the ink exchange apparatus, FIG. 4(b) is a side view of the printing unit consisting of inking rolls (an anilox roll and a rubber roll), a printing cylinder and an impression roll, and FIG. 5 is a flow chart showing an operation of said ink exchange apparatus.
The printing unit of a flexographic printer is constructed as shown in FIGS. 4(a), (b). That is, numeral 28 designates the printing cylinder having a printing die 29 fitted around its outer circumferential face, numeral 30 designates an impression roll disposed opposingly to said printing cylinder 28, numeral 1 designates the anilox roll (inking roll) and numeral 2 designates the rubber roll (inking roll), all of which compose the printing unit.
Numeral 3 designates a flexographic ink and said flexographic ink 3 is supplied into a nip portion P between the anilox roll 1 and the rubber roll 2 from the ink tank 4a (or ink tank 4b) through an ink pump 7 and an ink supply pipe 8.
And the ink 3 supplied into the nip portion P is doctored by the rubber roll 2 and is transferred uniformly onto the outer circumferential face of the anilox roll 1 and is further transferred onto the printing die 29 by a contact of the surface of the anilox roll 1 and the printing die 29 fitted around the outer circumferential face of the printing cylinder 28.
On the other hand, a sheet 31, such as a corrugated board sheet, to be printed passes between the printing cylinder 28 and the impression roll 30 and comes in contact with the printing die 29, thus a desired printing is made on the sheet 31.
While the printing is being made, the ink 3a within the ink tank 4a is supplied into said nip portion P, and an excess ink 3a overflows from both ends of said nip portion P, flows down into end pans (ink reservoirs) 15a, 15b and returns to the ink tank 4a through return pipes (discharge pipes) 10a, 10b.
Thus, the ink 3a circulates in said ink circulation and supply mechanism while printing is made, and after a desired printing is finished, an order change (ink color change and printing die exchange) becomes necessary.
Said ink circulation and supply mechanism is further described concretely. Numerals 11a, 11b designate ink supply ports of the ink tanks 4a, 4b, numerals 5, 5 designate covers of the ink tanks on which said ink supply ports 11a, 11b are provided and numeral 12 designates a joint provided at the lower end portion of the ink supply pipe 8, and said joint 12 is fitted detachably to either one of the ink supply ports 11a, 11b.
Numeral 13 designates a filter provided in the middle of the ink supply pipe 8, numeral 7 designates an ink pump provided on the upper side of said filter 13 in the middle of said ink supply pipe 8 and numeral 14 designates an ink funneling device provided at the upper end portion of the ink supply pipe 8, and said ink funneling device is disposed immediately above the nip portion between the anilox roll 1 and the rubber roll 2.
Numerals 15a, 15b designate end pans disposed immediately below both end portions of the anilox roll 1 and the rubber roll 2, numerals 10a, 10b designate return pipes (discharge pipes) elongating from said end pans 15a, 15b, and numeral 10 designates a return pipe (discharge pipe) connecting to said return pipes 10a, 10b, and the lower end portion of said return pipe 10 connects to either one of return ports 6a, 6b of the ink tanks 4a, 4b.
Next, said wash liquid supply mechanism is described concretely. Numeral 16 designates a wash liquid pipe, and said wash liquid pipe 16 connects to the ink supply pipe 8 via a solenoid valve 18 and a T-type joint 17.
Next, said ink tank exchange mechanism is described concretely. Numeral 20 designates a joint elevating cylinder, numeral 21 designates a bucket driving cylinder, numeral 22 designates a holder driving cylinder, numeral 23 designates a holder, numeral 25 designates a waste liquid bucket and numeral 32 designates a bracket connecting the joint 12 and the return pipe 10.
The operation of the ink exchange apparatus at the time of an order change is as follows:
As shown in FIG. 4(a), the joint 12 and the return pipe (discharge pipe) 10 are connected each other by the bracket 12 and are movable together in any direction of front and rear, right and left or up and down.
In FIG. 5, (a), (b), (c) and (d) show a flow chart at the time of an ink exchange, wherein FIG. 5(A) shows a state of ink circulation and supply (state of ink supply start), FIG. 5(b) shows a state of ink recovery and FIG. 5(c) shows a state of ink washing by a wash liquid.
First, by stopping the ink pump 7, the ink circulation in the ink circulation passage is stopped, and as shown in FIG. 5(b), the ink is recovered into the ink tank 4a for a certain time by a timer setting.
Next, by a recovery finish signal, the bracket 32 connecting the joint 12 and the recovery pipe (discharge pipe) 10 is elevated and is moved back, and as shown in FIG. 5(c), the joint 12 and the lower end portion of the return pipe 10 are moved to a position aside the ink tank 4a, that is, a predetermined position above the waste liquid bucket 25, and are stopped.
In this state, the solenoid valve 18 is opened, wash liquid is automatically supplied toward the ink funneling device 14 through the ink supply pipe 8 of the ink circulation and supply passage from the wash liquid pipe 16 via the T-type joint 17, and the insides of the ink supply pipe 8 and the ink funneling device 14 are washed, and further the ink of the nip portion between the anilox roll 1 and the rubber roll 2, the ink in the end pans 15a, 15b and the ink in the return pipes 10a, 10b, 10 are washed off.
In the meantime, the anilox roll 1 and the rubber roll 2 are making idle running and the firstly used ink sticked on the outer circumferential faces of both rolls 1, 2 and on the insides of both roll shaft end portions and the end pans 15a, 15b are washed off.
At the same time, the wash liquid is automatically supplied to the direction of the ink tank 4a through the ink supply pipe 8 from the wash liquid pipe 16 via the T-type joint 17, and the ink of the insides of the ink supply pipe 8, the ink pump 7, the filter 13 and the joint 12 is also washed off.
With the operation as above, all the wash liquid is discharged into the waste liquid bucket 25 from the return pipes 10a, 10b, 10 and from the ink supply pipe 8 via the opening port joint 12. Supply of the wash liquid is controlled by a time adjustable timer etc., and with a signal given after a certain time passes, the solenoid valve 18 is closed and the supply of wash liquid is stopped. Even after the supply of wash liquid is stopped, each device is kept stopped in that state, recovery of the wash liquid is continued for a certain time, then by a signal from the timer of the recovery finish, the next operation is carried out.
That is, by moving the bracket 32, the joint 12 is moved to the ink supply port 11b of the ink tank 4b in which ink for the next new order is contained, and the end portion of the return pipe 10 is moved to the return port 6b of the ink tank 4b, respectively, the movement of the bracket 32 is stopped, then the bracket 32 is let down, and the joint 12 is moved to the ink supply port 11b as shown in FIG. 4(a) and is automatically connected thereto. Likewise, the end portion of the return pipe 10 is connected to the return port 6b.
In this state, the ink pump 7 is started, ink for the next new order is circulated in the ink circulation and supply passage and a printing by use of the ink of the new order is carried out.
In the ink exchange apparatus used in the flexographic printer in the prior art, as shown in FIGS. 4 and 5, upon finishing of a printing by use of ink of the previous order, the ink pump 7 is stopped, the circulating ink is recovered into the presently used ink tank (of the previous order), then the connection of the lower end portion of the ink circulation passage (the lower end portions of the ink supply pipe 8 and the return pipe 10) and the ink tank 4a is released, the lower end portion of the ink circulation passage is moved above the waste liquid bucket 25 by the ink tank exchange mechanism, the wash liquid supply mechanism is worked, the ink circulation passage is washed by the wash liquid, the turbid wash liquid after used for washing is discharged into the waste liquid bucket 25, then supply of the wash liquid is stopped and the turbid wash liquid is recovered for a certain time by a natural discharge. Then, the lower end portion of the ink circulation passage is connected to the ink tank 4b of the next new order and a printing by use of ink of the new order is commenced.
This means that after the supply of wash liquid is stopped, a natural discharge is carried out until the turbid wash liquid is recovered. For this reason, a considerable time is required for the recovery of wash liquid of the roll nip portion or the circulation passage. In actual cases where a preference is put on a productivity, however, a next printing (supply of ink) is reopened before the liquid recovery is completely made, and in such case, upon commencement of ink circulation, the residual wash liquid in the roll nip portion or in the circulation passage returns into the ink tank, the ink there is diluted so that the viscosity of ink is lowered or the ink of a new order is discolored by mixing of the residual ink of the previous order, hence there is such a problem that a printing quality is lowered or the ink of a new order becomes unusable.